This is a renewal application to continue development of a multi-channel auditory nerve stimulation system. The eventual goal is to evaluate such a device as an auditory prosthesis in man. There are two principal facets to the proposed program; the continuation of the hardware development, especially of the transdermal electronics package, and the evaluation of the acoustic perceptions arising from the multi-electrode stimulation, first in animals, then eventually in humans. Electrode implantation will continue in cats to develop and test electrode materials and configurations and to acquire surgical experience in auditory nerve implantation. The electronics package is now available in pilot run numbers; materials and techniques for encapsulating the electronics for survival in the physiological environment, and materials and design for an implantable disconnect plug interfacing electronics and electrodes will be developed. These components will be tested in vitro and in vivo in animals. When satisfactory and reliable hardware is available, implants will be made in human volunteers. The principal thrust of this project will be to establish the value and potential of a multichannel cochlear prosthesis as compared to the single channel prosthesis now extant. Protocol, stimulation patterns, and percept analysis in the human implants will be directed toward this objective.